Typically in a safety-critical system there are one or more system components having certain measures and techniques considered so critically important they are referred to as vital. In some domains such as the rail industry and the associated positive train control systems, a safety-critical system with improved vitality is implemented to ensure that the train control system does not fail ambiguously.
Positive train control systems are utilized to prevent unsafe movement, avoid train collision or separation, enforce speed restrictions, enforce wayside safety for rail workers, and so forth. In positive train control systems it is imperative that a safety-critical system be capable of redundant cross checking of events in order to detect when a fault (e.g., individual hardware failure, network failure, data corruption, anomalies, etc.) occurs and react accordingly to the fault in a timely and vital manner.